Known stud holders in prior-art stud welders are constructed to hold a stud, which can have a headlike, rotationally symmetrical enlargement formed on a shaft or shank to be welded to some workpiece. These prior-art stud holders generally comprise a plurality of clamping jaws in which the stud is held, after being fed to the stud holder, so that its shaft end projects out of the stud holder on the workpiece side of the clamping jaws.
Known stud holders and welders include those taught in U.S. Pat. No. 3,309,495. In the stud welder of this patent bolts or studs are supplied for welding to a workpiece one at a time separately by means of a plunger or ramming tool so that the free shaft end of the stud projects through the workpiece-side mouth or end of the clamping jaws. Here the supply passage for the studs is constructed cylindrically for the studs or bolts in the vicinity of the clamping jaws, and has appropriate dimensions so that the studs or bolts are gripped by the clamp jaws exclusively on the periphery.
There is a danger here, particularly with studs or bolts with small head height (thickness), that the studs or bolts, particularly under gravity, will tend to enter or be engaged by the clamp jaws with their free ends slanted downwardly. Thus these incorrectly oriented studs or bolts may be gripped by the clamp jaws and welded in this incorrect orientation.
This danger is even greater when the studs or bolts are supplied by air pressure.